Researchers from Johns Hopkins University in Baltimore believe that people living with HIV Subtype D have an increased risk of dementia compared with those with other subtypes of the virus, reports United Press International. Subtype D is rare in the United States and is more prominent in Eastern and Central Africa.

According to the scientists, this study—reported in the journal Clinical Infectious Diseases—is the first to establish a connection between Subtype D and cognitive impairment, a common complication of uncontrolled HIV infection.

There are multiple forms of HIV, which are specified by small differences in the virus's genetic sequence and named by letters A through K.